‘What’s going to happen when he’s older? When he’s too big for even me to handle? Will he kill someone? Maim them? What happens when I’m dead? Where will he go … ?” Ben, the narrator of this darkly comic debut from Jem Lester, is brooding about the future of his much-loved and profoundly autistic 11-year-old son. Jonah has no speech, and his only means of communicating his needs is by selecting pictures on laminated cards.

When he is stressed, frightened or frustrated Jonah bites his hands until they bleed. He hurts himself and other people, even those he loves the most. He is doubly incontinent. Shtum traces the long war his parents fight to get local authority funding for an eye-wateringly expensive specialist residential school. It is their only hope for Jonah’s future happiness as he has made no progress in primary school.

This is not the kind of autism familiar from Rain Man and The Curious Incident of the Dog in the Night-Time, where the central characters’ obsessions, sensory idiosyncracies and social difficulties can be understood with a little sympathy and imagination. Jonah’s inner world is a baffling mystery even to those who observe him most closely. The 25%-30% of autistic people who never develop language rarely make it into fiction or on to our screens.

Jonah is no mere cipher but a very real boy: he adores twirling feathers, hot bubble baths and Marmite on toast. He is unpredictable, has no sense of danger and needs constant vigilance. His parents ricochet between love, guilt, exhaustion and rage. As the novel opens, Ben’s wife Emma suggests Ben moves out with Jonah on the basis that being a single father will make their son’s need for a residential school more urgent.

Shtum, the Yiddish word for keeping silent or hiding secrets, is the perfect title for a novel in which even those who can speak do not share their thoughts with each other. Ben is a copywriter whose alcoholism lost him his job, now slumming it in his father’s catering supply business. As if that wasn’t bad enough, he is forced to move back in with his father, Georg, a Holocaust survivor who has never made any bones about how much he dislikes his son’s self-pity and inability to see a job through to the end.

It makes for an uneasy household. Georg’s tenderness towards his wordless autistic grandson is both welcome and resented; he tells Jonah bedtime stories of his youth escaping the Nazis, tales never shared with his own son. Meanwhile, Emma, a seemingly successful lawyer, is keeping her own counsel. She doesn’t answer calls, leaving her estranged husband filled with suspicion and jealousy. At first a shadowy, unsympathetic figure, she becomes fully realised as the novel develops.

Lester doesn’t spare his main character: Ben isn’t an idealised hero battling for his disabled son’s rights. His failings are laid out in plain sight. He is a man-boy who has never quite grown up. At one point he reflects: “I’m wearing a costume, shuffling around in oversized shoes, playing the role of an adult.” This is the literary territory of Tony Parsons and Nick Hornby, infused with the Jewish humour of Howard Jacobson and Shalom Auslander.

The novel’s text is broken up with officious letters from authorities, crammed with Orwellian doublespeak. It is also peppered with ironically deployed icons of the type Jonah uses to communicate. At times Lester’s ambitious cinematic crosscutting between showdowns with officialdom and stories from the past puts a strain on the narrative flow. Overall, though, this is an impressive novel that gives a very accurate portrayal of the struggles some families of autistic children endure, while taking the reader on an exhilarating roller coaster ride between pathos, comedy and anger.

What does the drama get right and wrong about autism? As the dad of an ‘autie’, Simon Hattenstone wonders where the laughs are – while his daughter Maya finds a birthday party meltdown all too familiar